Many semiconductor products contain important data which have to be kept secret, like codes for encryption or identification. Examples are chips in banking cards, for ticketing or pay TV applications. Chips which are used in such fields might need to be security certified to prove a certain security standard. Sufficient resistance against all kinds of attacks which aim at retrieval of codes or against uncontrolled change of functionality has to be implemented. Possible attack scenarios can be grouped in sensing attacks and forcing attacks. Sensing attacks are all trials to get the secret information from the chip by measuring certain signals from the chip like current consumption, electromagnetic emission, or voltage probing of signal lines. Forcing attacks try to change the operation conditions and draw conclusions from the resulting behavior of the chip.
Security chips may use several sensors to detect such attack attempts, e.g. checking environmental conditions (like supply voltage, temperature, and light exposure). With the availability of high sophisticated equipment timely resolved probing of single wires of a chip becomes more and more a realistic attack scenario. Also, forcing internal signals at certain time points becomes possible. Some signals are of higher or special interest as they might give access to the most secret information. These are e.g. data busses and wires connected to the latches storing the secret keys. As global sensors are not able to detect such local attacks, these signals need a dedicated protection.
Thus, there may be a need for an improved detection arrangement being capable to detect such local attacks for providing a protection for such signals.